Iontophoresis is a method for delivering a drug across a biological membrane, such as the skin or, in the case of certain ear surgery procedures, the tympanic membrane (TM). By applying low-level electrical current to a similarly charged drug solution, iontophoresis repels ions of the drug, thus transporting them across the skin or other membrane. In ear procedures, attempts have been made in the past to use iontophoresis to anesthetize (or “numb”) a TM before placing an ear tube across it to treat chronic ear infections. For TM iontophoresis, a drug solution is placed in an ear canal and current is applied to the solution via an electrode, thus transporting the anesthetizing drug across the TM.
Prior iontophoresis devices and systems have had limited success and often cannot be used in all patients. Prior devices generally do not seal the drug solution in an ear canal, thus requiring a patient to recline and tilt his/her head during an iontophoresis procedure. Using currently available iontophoresis methods, the patient must remain relatively motionless in this reclined, head-tilted position for 5-15 minutes while the iontophoresis procedure provides adequate anesthesia to the TM, which can be especially difficult for children. Furthermore, using the currently available systems it is only possible to anesthetize one ear at a time, thus making iontophoretic anesthesia of both TMs in a patient a relatively lengthy, uncomfortable process.
Attempts have been made to administer iontophoretic fluid to a TM via an earplug designed to hold the fluid in the ear canal. For example, see U.S. Pat. No. 5,674,196, issued to Donaldson et al. Earplugs such as the one described in Donaldson and other currently available earplugs, however, have a number of shortcomings. For example, most earplugs are designed to keep fluid out of the ear canal, rather than in the ear canal. Currently available and previously described earplugs generally do not conform adequately to the curved anatomy of the ear canal and thus do not form a good seal in the ear canals of at least some (and in some cases all) patients. Thus, current earplugs typically allow fluid to leak out of the ear, which makes iontophoretic anesthesia delivery difficult if not impossible with the patient in an upright position. Furthermore, previously described earplug devices for use in iontophoresis have not addressed issues such as bubble formation in the iontophoretic drug solution, which bubbles may interfere with the contact between an iontophoretic electrode and the solution.
Therefore, it would be advantageous to have improved devices and systems for administering iontophoresis to a tympanic membrane. Ideally, such devices and systems would allow iontophoretic anesthesia to be administered to a patient in an upright position. Also ideally, such devices and systems would facilitate bilateral, simultaneous TM iontophoresis. At least some of these objectives will be met by the embodiments of the present invention.